JP2022536101A - Planetary reducer with at least one axial force transmission component forming a radially eccentric force path - Google Patents

Abstract

The present invention relates to a speed reducer (1) for an electric parking brake, said speed reducer (1) comprising a drive shaft (3), at least one reduction stage and a cylindrical body (14), said cylindrical body ( 14) forms a screw-nut mechanism together with the outer planetary gear (2) of the speed reducer. The speed reducer (1) converts the axial force applied through either the bearing ring (20) or the cylindrical body (14) of the drive shaft (3) to the bearing ring (20) or the cylindrical body (14). ), at least one axial force transmission component (16, 11) located between said bearing ring (20) and said cylindrical body (14). Such axial force transmission components (16, 11) prevent buckling of the drive shaft (3) by defining a radially eccentric axial force transmission path.

Description

The present invention relates to planetary reduction gears, for example for electric parking brake actuators of motor vehicles.

A conventional floating caliper electric parking brake is disclosed in US Pat.

In a known manner per se, the brake of FIG. 1 comprises a planetary gear reducer, the external sun gear of which forms a piston 100 translatably movable along the longitudinal axis A100. The input torque generated by the electric motor is transmitted to the piston 100 via a drive shaft 200, shown separately in FIG. 2, and a series connected planetary gear train. The output planet carrier 300 of the speed reducer has external threads. This external thread cooperates with the internal thread formed by internal thread 400 of piston 100 to convert rotation of planet carrier 300 into translation of piston 100 along longitudinal axis A100. Such translation allows the brake pads to be pressed against the brake disc by cooperating with the caliper fingers 500 arranged facing the piston 100 .

In this conventional speed reducer, the drive shaft 200 carries a sun gear 600 which meshes with the planetary gears 700 of the first gear train. The first gear train planet carrier 900 carries a sun gear 950 which meshes with the second gear train planet gears 970 . Drive shaft 200 includes a downstream portion 800 that passes through openings in planet carrier 900 and sun gear 950 so that one end thereof is received within a cavity in output planet carrier 300 . This allows the shaft 200 to rotate relative to the planet carriers 300 and 900 and relative to the sun gear 950 .

In this configuration, when mechanical forces are applied to the piston 100 during braking, the forces are recovered by the drive shaft 200 . This force can cause shaft 200 to buckle.

French Patent Application No. 3031058

One object of the invention is to limit the risk of buckling of the drive shaft of such a planetary reducer, in particular in order to allow a reduction in the diameter of the drive shaft thereof.

More generally, the present invention aims at reducing the mass and cost of such planetary reducers.

To this end, one subject of the invention is
a drive shaft rotatable about a longitudinal axis by a motor, the drive shaft comprising an internal sun gear having the longitudinal axis as its axis of rotation;
an external sun gear having internal teeth forming internal threads, the external sun gear being rotatably fixed about said longitudinal axis;
a gear comprising one or more planet carriers and one or more planet gears carried by said one or more planet carriers;
a cylindrical body configured to be rotationally driven about the longitudinal axis by the gear when the drive shaft is rotated about the longitudinal axis, wherein the cylindrical body is configured to rotate about the longitudinal axis; a cylinder having external threads that cooperate with the internal threads of the external sun gear such that rotation about an axis drives the external sun gear in translation along the longitudinal axis;
A planetary reduction gear comprising:

According to the invention, said drive shaft comprises a shoulder forming a bearing ring radially outwardly of said internal sun gear, wherein the axial force exerted on one of said bearing ring and said cylindrical body is reduced by said bearing ring. and the other of the cylinders, the speed reducer comprises at least one axial force transmission component interposed between the bearing ring and the cylinder.

Said at least one transmission part is adapted to recover part of the axial force exerted on said reducer in order to relieve said drive shaft during braking, for example when said reducer belongs to a brake actuator. to enable.

The invention thus makes it possible to reduce the mass and cost of said reducer compared to conventional reducers by reducing the diameter of the drive shaft, in particular of the part adjacent to its bearing ring.

In one embodiment, said at least one axial force transmission component, preferably via a friction washer, bears on the one hand the bearing ring and on the other hand one of the planet carriers of the gear wheel. obtain.

In one embodiment, said at least one axial force transmission component may comprise one or more radial openings, each said radial opening forming a housing for each planetary gear of said gear. do.

In one embodiment, said at least one axial force transmission component comprises arms, said arms defining said radial openings therebetween.

In one embodiment, said gear comprises a first planet carrier and a second planet carrier, wherein an axial force exerted on one of said bearing ring and said first planet carrier is controlled by said bearing ring and said second planet carrier. said speed reducer comprising a first axial force transmission component interposed between said bearing ring and said first planet carrier for transmission to the other of said one planet carriers; said second planet carrier for transmitting an axial force exerted on one of said planet carrier and said cylindrical body to the other of said first planet carrier and said cylindrical body, said second planet carrier forming a second axial force transmission component interposed between the planet carrier and said cylindrical body.

In one embodiment, the speed reducer comprises a ring gear rotatably integral with the external sun gear about the longitudinal axis, and the second planet carrier comprises the ring gear. forming a free cage carrying planetary gears meshing with both internal teeth and internal teeth of said cylinder, said internal teeth of said ring gear having a different number of teeth than said internal teeth of said cylinder; have.

In one embodiment, said second axial force transmission part presses against said first planet carrier on the one hand, preferably via friction washers, and on the other hand, preferably via friction washers, on said cylindrical body can press the bearing surface of

Another object of the invention is an electric brake actuator comprising a speed reducer as described above and an electric motor arranged to drive the drive shaft in rotation about the longitudinal axis.

Another subject of the invention is a disc brake, preferably a floating caliper brake such as a parking brake or service brake, comprising an electric brake actuator as described above.

Another subject of the invention is a motor vehicle equipped with a disc brake as described above.

Other advantages and features of the present invention will become apparent from the detailed non-limiting description that follows.

The following detailed description refers to the accompanying drawings.

FIG. 1 is a schematic partial longitudinal section of an electric parking brake with a planetary reduction gear of known type. 2 is a schematic perspective view of a drive shaft of the brake reducer of FIG. 1; FIG. FIG. 3 is a schematic partial longitudinal section of a planetary reduction gear according to the invention. 4 is a schematic perspective view of an axial force transmission portion of the speed reducer of FIG. 3. FIG. 5 is a schematic partially exploded perspective view of the speed reducer of FIG. 3. FIG.

Figures 3 and 5 show a planetary gear 1 according to the invention. This reducer 1 can be used in the automotive field, for example in electric brakes mounted on disk brakes, in particular floating caliper type disk brakes, or more generally for converting rotary motion into translational motion. It is an electromechanical actuator for

Referring to FIG. 3, the reducer 1 comprises an external sun gear 2 forming a piston translatably movable along a longitudinal axis A1. This piston 2 is fixed against rotation about said longitudinal axis A1 by any conventional means, for example by inserting a pin belonging to the brake caliper into a corresponding notch made in the piston 2. there is

Translational movement of the piston 2 along the longitudinal axis A1 is caused by an electric motor (not shown) that transmits input torque to the drive shaft 3 of the reducer 1. Rotational motion of the shaft 3 about the axis A1 is converted into translational motion of the piston 2 via gears and motion converting members described below.

More specifically, in this embodiment the drive shaft 3 is adapted to be connected to an electric motor, the connection being such that when the shaft of said motor rotates about axis A1, the drive shaft 3 It is designed to be rotationally driven about the axis A1.

The drive shaft 3 comprises a first internal sun gear 4 rotatably integral with this shaft 3 about axis A1. In this embodiment the sun gear 4 and the shaft 3 are formed as a single piece.

The external sun gear 2 is provided with internal teeth 5 which form circumferentially spaced longitudinal grooves for meshing with the planetary gears while ) forming an internal thread configured to cooperate with the external thread.

The reducer 1 comprises a first planetary carrier 6 which includes three openings 7 eccentric to the axis A1 and at 120° to each other. Each of these openings 7 receives a journal 8 carrying a respective planetary gear 9 in order to reliably guide the rotation of the respective planetary gear 9 (see FIG. 5).

Said planetary gear 9 meshes both with the first internal sun gear 4 and with said longitudinal groove formed by the internal teeth 5 of the external sun gear 2 . Consequently, the rotation of the sun gear 4 of the shaft 3 about its axis A1 drives each planetary gear 9 in rotation about its journal 8, while each postal gear 9 rotates about its axis A1. It is rotationally driven along a circumferential orbit and thus the first planet carrier 6 is rotationally driven about the axis A1.

The reducer 1 thus makes it possible to drive the first planetary carrier 6 in rotation about the longitudinal axis A<b>1 at a rotational speed lower than that of the drive shaft 3 .

In the examples of FIGS. 3 and 5 the reduction gear 1 comprises a second reduction stage. Its input consists of a second internal sun gear 10 carried by the first planet carrier 6 . The sun gear 10 is integrated with the planetary carrier 6 so as to be rotatable about the axis A1. In this embodiment the sun gear 10 and the planet carrier 6 are formed as a single piece.

The reducer 1 of FIGS. 3 and 5 comprises a second planetary carrier 11 . A second planetary carrier 11 forms a free cage carrying three planetary gears 12 in this example. In a known manner, the cage 11 has a generally tubular shape and includes radial openings extending respectively in the axial central portion, so that each radial opening extends into each axial end portion on either side of the cage. is axially defined by Each of these radial openings form a housing for one of the planetary gears 12 . A respective shaft is axially passed through each opening to carry each planetary gear 12 and positively guide their rotation. These shafts are received in corresponding holes in both axial end portions of the cage and are thereby connected to the cage.

Referring to FIG. 3, the speed reducer 1 comprises a ring gear 13 with external and internal teeth. This external toothing engages in said longitudinal groove formed by the internal toothing 5 of the external sun gear 2 . Therefore, the ring gear 13 and the external sun gear 2 are integrated with each other so as to be rotatable about the axis A1. The inner teeth of the ring gear 13 are configured to mesh with the planetary gears 12 defining contact points located radially inwardly with respect to the inner teeth 5 of the outer sun gear 2 . That is, the internal teeth of the ring gear 13 are configured to offset the longitudinal groove formed by the internal teeth 5 of the external sun gear 2 radially inward of the reducer 1 .

In this embodiment, the planetary gear 12 also meshes with teeth formed in the cavity of the motion converting member 14, thereby necessitating the radial offset. This cavity has a radial dimension smaller than the radial inner dimension of the outer sun gear 2 (see Figure 3 and below).

In this embodiment the motion converting member 14 takes the form of a cylinder with external threads 15 . The external thread 15 cooperates with the internal thread formed by the internal toothing 5 of the external sun gear 2 . As a result of this cooperation, rotational movement of cylinder 14 about axis A1 results in translational movement of external sun gear 2 along axis A1. The cylinder 14 and the piston 2 thus form a reversible screw-nut mechanism.

Said cavity of the cylindrical body 14 is configured to accommodate a portion of the cage 11 in which the planetary gear 12 meshes through its first axial portion with teeth formed in this cavity. It's like

The ring gear 13 is axially adjacent to the cylinder 14 , so that the planetary gear 12 meshes with the internal teeth of the ring gear 13 via its second axial portion.

Thanks to this configuration, when the sun gear 10 rotates about the axis A1, each planetary gear 12 is driven to rotate about its own axis of rotation, while rotating along a circumferential orbit about the axis A1. As a result, the free cage 11 is rotationally driven about the axis A1.

If the number of internal teeth of ring gear 13 is the same as the number of teeth formed in the cavity of cylinder 14, rotation of sun gear 10 about axis A1 causes cylinder 14 to rotate about its axis A1. Do not rotate. In fact, the teeth of the cylinder 14 are then axially aligned with the internal teeth of the ring gear 13, so that the planet gears 12 simply roll within the teeth of the cylinder 14 when rotating. be.

Therefore, in this embodiment, the ring gear 13 has fewer internal teeth than the number of teeth formed in the cavity of the cylindrical body 14, thereby achieving a relatively large speed reduction rate.

The reducer 1 thus makes it possible to drive the cylindrical body 14 in rotation about the longitudinal axis A1 at a rotational speed which is lower than that of the sun gear 10 and even lower than that of the drive shaft 3. be possible.

Therefore, the speed reducer 1 reduces the rotational speed by increasing the torque.

The invention makes it possible to recover the axial force exerted on the speed reducer 1, for example when the piston 2 exerts a braking force.

For this purpose, the speed reducer 1 comprises a force transmission component 16 as shown in FIG.

In this example, said part 16 has a generally tubular shape, which is dimensioned to allow passage of the drive shaft 3 and to allow relative rotation of the shaft 3 with respect to the part 16. A central opening 19 is defined.

In this embodiment, the force transmission component 16 comprises an annular, circumferentially solid first portion 17 and a second portion comprising three axially extending arms 18 . Arms 18 define radial openings between them, each opening forming a housing for a respective planetary gear 9 .

To achieve force recovery, the drive shaft 3 is provided with a shoulder 20 forming a bearing ring radially outside the internal sun gear 4 .

The part 16 is sandwiched between the bearing ring formed by the shoulder 20 of the shaft 3 and the planet carrier 6 . This transmits the axial force exerted on the planet carrier 6 to the bearing ring 20 or from the bearing ring 20 to the planet carrier 6 while at the same time this axial force acts on the axis of the radially central portion of the shaft 3 , in particular the shoulder 20 . This is to prevent passing through parts located on both sides of the direction. As a result, the risk of buckling of the drive shaft 3 when using the reducer 1 is greatly reduced or eliminated.

More precisely, said first part 17 of the force-transmitting part 16 forms a bearing surface 21 which bears via a friction washer 23 against a bearing surface 22 formed by the bearing ring 20 . do. Axial arm 18 of force transmission component 16 defines a bearing surface 24 which bears against bearing surface 25 of planet carrier 6 .

The friction washer 23 makes it possible to limit the wear of the bearing ring 20 and the force transmission part 16 as they rotate relative to each other.

Moreover, the two axial end portions of the free cage 11 each form a bearing surface 26 , one bearing, via a friction washer 28 , against a bearing surface 27 of the planet carrier 6 and the other a friction washer 29 . presses against the bearing surface formed by the bottom of said cavity of cylinder 14 via .

The free cage 11 thus interposed between the planet carrier 6 and the cylinder 14 forms a second axial force transmission part by means of which the axial force exerted on the cylinder 14 is reduced. Forces can be transmitted to the planet carrier 6 or, conversely, axial forces acting on the planet carrier 6 can be transmitted to the cylinder 14 .

Friction washers 28 and 29 make it possible to limit the wear of planet carrier 6, free cage 11 and member 14 as they rotate relative to each other.

Thus, according to the embodiment of FIG. 3, the axial force exerted on the cylinder 14, such as when the piston 2 is subjected to a braking force, is reduced to two axial forces interposed between the bearing ring 20 and the cylinder 14. While transmitting to the bearing ring 20 via the transmission parts 11 and 16, the path of this axial force is relatively It is possible to prevent passage through parts with a small diameter. The ability to transmit forces via this eccentric path is also ensured when forces in the other direction, ie axial forces, are applied to the bearing ring 20 . In that case, the two axial force transmission parts 11 and 16 enable the axial force exerted on the bearing ring 20 to be transmitted to the cylinder 14 .

The above description is offered by way of example and is in no way limiting. For example, in an embodiment not shown here, the speed reducer 1 may comprise a single speed reduction stage. In this case the planet carrier 6 does not comprise the second internal sun gear 10 and is directly connected to the cylinder 14, so that the cylinder 14 and the planet carrier 6 are integral with each other so as to be rotatable about the axis A1. It's becoming Of course, in such a single-stage reduction embodiment, the speed reducer 1 does not include the free cage 11, the planet gears 12, and the friction washers 28 and 29.

In other embodiments not shown here, the speed reducer 1 comprises a second speed reduction stage different from the one presented by way of example in FIG. For example, planetary gear 12 is carried directly by member 14 rather than by free cage 11 . In order to ensure recovery of the axial forces between the planet carrier 6 and this member 14, in this case the speed reducer 1 is sandwiched between the planet carrier 6 and the member 14, similar to the part 16 Additional axial force transmission components may be provided.

A100 longitudinal axis 100 external sun gear/piston 200 drive shaft 300 output planet carrier 400 internal teeth of external sun gear 500 caliper fingers 600 sun gear 700 planet gears 800 downstream portion of drive shaft 900 first gear train planet carrier A1 longitudinal axis 1 planetary reducer 2 external sun gear/piston 3 drive shaft 4 first internal sun gear 5 internal teeth of external sun gear 6 first planet carrier 7 opening for journal of first planet carrier Part 8 Journal of first planet carrier 9 Planetary gear of first planet carrier 10 Second internal sun gear 11 Second planet carrier/free cage/second axial force transmission part 12 Second planet carrier Planetary Gear 13 Ring Gear 14 Cylinder/Motion Converting Member/Screw 15 External Thread of Cylinder 16 (First) Axial Force Transmission Part 17 First Part/Solid Part of Axial Force Transmission Part 18 Axial Force Transmission Second part/arm of part 19 Central opening of axial force transmission part 20 Shoulder/bearing ring of drive shaft 21 Bearing surface of axial force transmission part 22 Bearing surface of bearing ring 23 Friction washer 24 Axial force transmission Bearing surface of component 25 Bearing surface of first planet carrier 26 Bearing surface of second planet carrier 27 Bearing surface of first planet carrier 28 Friction washer 29 Friction washer

Claims (10)

A drive shaft (3) arranged to be rotatably driven by a motor about a longitudinal axis (A1), the inner sun arranged to rotate about said longitudinal axis (A1). a drive shaft (3) comprising a gear (4);
an external sun gear (2) with internal teeth (5) forming an internal thread, the external sun gear (2) being rotatably fixed about said longitudinal axis (A1);
a gear comprising one or more planet carriers (6, 11) and one or more planet gears (9, 12) carried by said one or more planet carriers (6, 11);
A cylindrical body (14) configured to be rotationally driven about said longitudinal axis (A1) by said gear when said drive shaft (3) is rotated about said longitudinal axis (A1). such that rotation of this cylinder (14) about said longitudinal axis (A1) drives said external sun gear (2) in translation along said longitudinal axis (A1) , a cylinder (14) with an external thread (15) cooperating with the internal thread of the external sun gear (2);
A speed reducer (1) comprising
said drive shaft (3) comprising a shoulder (20) forming a bearing ring radially outwardly of said internal sun gear (4), one of said bearing ring (20) and said cylindrical body (14); A speed reducer (1) is provided between said bearing ring (20) and said cylindrical body (14) to transmit axial forces applied to said bearing ring (20) and said cylindrical body (14) ), comprising at least one axial force transmission component (16) interposed between . Said at least one axial force transmission part (16) is attached to said bearing ring (20) on the one hand, preferably via a friction washer (23) and on the other hand to one of the planetary carriers of one or more gear wheels. A reduction gear (1) according to claim 1, which compresses the Said at least one axial force transmission component (16) comprises one or more radial openings each forming a housing for each planetary gear (9) of said gear. A speed reducer (1) according to claim 1 or 2, wherein the A reducer (1) according to claim 3, wherein said at least one axial force transmission component (16) comprises arms (18), said arms (18) defining said radial openings therebetween. ). said gear comprises a first planet carrier (6) and a second planet carrier (11), wherein the axial force exerted on one of said bearing ring (20) and said first carrier (6) is reduced by: The speed reducer (1) is coupled between the bearing ring (20) and the first planet carrier (6) for transmission to the other of the bearing ring (20) and the first planet carrier (6). ), the axial force applied to one of said first planet carrier (6) and said cylindrical body (14) being transferred to said first planet carrier (6) and said cylindrical body (14). Said second planet carrier (11) connects said first planet carrier (6) and said cylinder ( Reducer (1) according to any of the preceding claims, forming a second axial force transmission part interposed between 14). comprising a ring gear (13) rotatably integral with said external sun gear (2) about said longitudinal axis (A1), said second planet carrier (11) supporting said ring Forming a free cage carrying a planetary gear (12) meshing with both the internal teeth of gear (13) and the internal teeth of said cylindrical body (14), said internal teeth of said ring gear (13) 6. Reducer (1) according to claim 5, having a number of teeth different from the number of teeth of said internal teeth of body (14). Said second axial force transmission part (11) presses against said first planet carrier (6) on the one hand preferably via a friction washer (28) and on the other hand preferably a friction washer (29). 7. A reduction gear (1) according to claim 5 or 6, wherein the bearing surface of said cylindrical body (14) is pressed through. A speed reducer (1) according to any one of claims 1 to 7, and an electric motor configured to rotationally drive the drive shaft (3) about the longitudinal axis (A1), Electric brake actuator. Disc brake, preferably a floating caliper brake, comprising an electric brake actuator according to claim 8. A motor vehicle comprising a disc brake according to claim 9.

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